Herbicidal compositions

ABSTRACT

The invention relates to a method for controlling the growth of weeds at a locus which comprises applying to said locus: (a) 2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione, or an agriculturally acceptable salt or metal complex thereof; and (b) a triazine herbicide with the exclusion of atrazine; and their use as herbicides.

[0001] This invention relates to new herbicidal compositions comprisinga mixture of a benzoyl cyclohexanedione and herbicidal 1,3,5-triazine or1,2,4-triazinone compounds. It also relates to the use of the mixtureper se and to a method of controlling weeds.

[0002] The above compounds are already known in the art as herbicides.1,3,5-Triazine and 1,2,4-triazinone herbicides (hereinafter referred toas the triazine herbicides) are well known in the art and includeametryn (N²-ethyl-N⁴-isopropyl-6-methylthio-1,3,5-triazine-2,4-diamine),atrazine (6-chloro-N²-ethyl-N⁴-isopropyl-1,3,5-triazine-2,4-diamine),aziprotryne (4-azido-N-isopropyl-6-methylthio-1,3,5-triazin-2-ylamine),cyanazine[2-(4-chloro-(ethylamino)1,3,5-triazin-2-ylamino)-2-methylpropionitrile],methoprotryne[N²-isopropyl-N⁴-methoxypropyl)-6-methylthio-1,3,5-triazine-2,4-diamine],metribuzin (4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one),prometryn (N²,N⁴-di-isopropyl-6-methylthio-1,3,5-triazine-2,4-diamine),prometon (N²,N⁴-di-isopropyl-6-methoxy-1,3,5-triazine-2,4-diamine),propazine (6-chloro-N²,N⁴-di-isopropyl-1,3,5-triazine-2,4-diamine),simetryn (N²,N⁴-diethyl-6-methylthio-1,3,5-triazine-2,4-diamine),simazine (6-chloro-N²,N⁴-diethyl-1,3,5-triazine-2,4-diamine),terbuthylazine(N²-tert-butyl-6-chloro-N⁴-ethyl-1,3,5-triazine-2,4-diamine), terbutryn(N²-tert-butyl-N⁴-ethyl-6-methylthio-1,3,5-triazine-2,4-diamine) andtrietazine (6-chloro-N²,N²,N⁴-triethyl-1,3,5-triazine-2,4-diamine), andare disclosed for example in “The Pesticide Manual”, 12th edition, 2000(British Crop Protection Council) and earlier editions, as selectiveherbicides. Herbicidal 4-benzoylisozaxoles of formula (I) below aredisclosed in European Patent (Application) Publications No. 0418175,0487357, 0527036 and 0560482.

[0003] Herbicidal benzoyl cyclohexanediones are disclosed in theliterature, for example European Patent Publication No. 0186118. Inparticular U.S. Pat. No. 5,506,196 discloses 2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione.

[0004] It has been found that the use of triazine herbicides incombination with certain benzoyl cyclohexan dione derivatives, extendsthe spectrum of herbicidal activity without loss of crop selectivity.Therefore the said combinations represent an important technologicaladvance. The term “combination” as used in this specification refers tothe “combination” of a benzoyl cyclohexanedione herbicide and a triazineherbicide.

[0005] The invention also seeks to provide a herbicidal compositionwhich allows lower dose rates of triazine herbicides to be applied tothe environment without reducing (and preferably increasing) the levelof weed control.

[0006] The present invention provides a method for controlling thegrowth of weeds (i.e. undesired vegetation) at a locus which comprisesapplying to the locus a herbicidally effective amount of.

[0007] (a) a benzoyl cyclohexanedione of formula (I):

[0008]  which is2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione, or anagriculturally acceptable salt or metal complex thereof; and

[0009] (b) a triazine herbicide with the exclusion of atrazine.

[0010] The triazine herbicide and benzoyl cyclohexanedione are normallyused in the form of herbicidal compositions (i.e. in association withcompatible diluents or carriers and/or surface-active agents suitablefor use in herbicidal compositions), for example as hereinafterdescribed.

[0011] Preferably the triazine herbicide is a compound of the formula(II):

[0012] wherein R¹ represents chlorine or straight- or branched chainalkylthio or alkoxy having from one to six carbon atoms; R² representsazido, monoalkylamino, dialkylamino or cycloalkylamino, in which thealkyl or cycloalkyl moieties may be optionally substituted by one ormore substituents selected from cyano and alkoxy; and R³ representsstraight- or branched-chain N-alkylamino having from one to six carbonatoms;

[0013] or of formula (III):

[0014] wherein R¹ is as defined above and R⁴ represents straight- orbranched chain alkyl having from one to six carbon atoms.

[0015] More preferably R¹ represents chlorine or methylthio and R³represents straight- or branched-chain N-alkylamino having from one tofour carbon atoms.

[0016] Compositions containing compounds of formula (II) above whereinR² represents azido, straight- or branched-chain N-alkylamino havingfrom one to four carbon atoms (wherein th alkyl moiety is optionallysubstituted by cyano or methoxy) are preferred.

[0017] Further preferred compounds of formula (II) above are those inwhich R³ represents N-(t-butyl)amino, R² represents N-ethylamino and R¹represents chlorine or methylthio, which are known respectively asterbuthylazine and terbutryn.

[0018] Preferred compounds of formula (II) above are those in which R¹represents chlorine, R³ represents N-ethylamino and R² representsN-ethylamino or N-(2-methylpropanenitrile)amino, known respectively assimazine and cyanazine; cyanazine being most preferred.

[0019] A preferred compound of formula (III) above is the compound inwhich R¹ represents methylthio, R⁴ represents tert-butyl, which is knownas metribuzin.

[0020] The amounts of the triazine herbicide and benzoylcyclohexanedione applied vary depending on the the weeds present andtheir population, the compositions used, the timing of the application,the climatic and edaphic conditions, and (when used to control thegrowth of weeds in crop growing areas) the crop to be treated. Ingeneral, taking these factors into account, application rates from 5 gto 500 g of benzoyl cyclohexanedione and from 250 g to 5000 g of thetriazine herbicide per hectare give good results. However, it will beunderstood that higher or lower application rates may be used, dependingupon the problem of weed control encountered.

[0021] For the selective control of weeds at a locus of weed infestationwhich is an area used, or to be used, for growing of crops applicationrates from 5 g to 500 g of benzoyl cyclohexanedione and from 250 g to5000 g of the triazine herbicide per hectare are particularly suitable,preferably from 25 to 150 g of benzoyl cyclohexanedione and from 500 gto 1500 g of the triazine herbicide per hectare. When applied to acrop-growing area, the rate of application should be sufficient tocontrol the growth of weeds without causing substantial permanent damageto the crop.

[0022] The combined use described abov may be used to control a verywide spectrum of annual broad-leafed weeds and grass weeds in crops,e.g. maize and plantatation crops such as sugar cane, withoutsignificant permanent damage to the crop. The combined use describedabove offers both foliar and residual activity and consequently can beemployed over a long period of crop development, i.e. from pre-weedpre-crop emergence to post-weed post-crop emergence.

[0023] In the method according to this feature of the present inventionthe combined use of (a) and (b) to control grass weeds in maize ispreferred.

[0024] Where the triazine herbicide is ametryn the combined use of (a)and (b) to control grass weeds in sugar cane is also preferred.

[0025] In the method described above, the combined use of (a) and (b) inproportions of 2:1 to 1:1000 wt/wt of (a): (b) is preferred, proportionsof 1:3 to 1:60 wt/wt (or 1:3.3 to 1:60 wt/wt) being particularlypreferred.

[0026] By the term ‘pre-emergence application’ is meant application tothe soil in which the weed seeds or seedlings are present beforeemergence of the crop. By the term ‘post-emergence application’ is meantapplication to the aerial or exposed portions of the weeds which haveemerged above the surface of the soil. By the term foliar activity ismeant herbicidal activity produced by application to the aerial orexposed portions of the weeds which have emerged above the surface ofthe soil. By the term ‘residual activity’ is meant herbicidal activityproduced by application to the soil in which weed seeds or seedlings arepresent before emergence of the weeds above the surface of the soil,whereby seedlings present at the time of application or which germinatesubsequent to application from seeds present in the soil, arecontrolled.

[0027] In the present invention, PPI or pre-emergence applications arepreferred, and pre-emergence application of the benzoyl cyclohexanedioneand triazine herbicide is most preferred.

[0028] Preferably the combination of benzoyl cyclohexanedione andtriazine herbicide is applied to an area used, or to be used, for thegrowing of a crop, for exampl maize, sugarcane or plantation crops.Preferably the crop is maize.

[0029] In accordance with the usual practice, a tank mix may be preparedprior to use by combining separate formulations of the individualherbicidal components.

[0030] The following non-limiting experiments illustrate the presentinvention.

EXAMPLE 1

[0031] Seed of various broad-leaf and grass weed species were sown inunsterilised clay loam soil. The soil surface was then sprayed withranges of concentrations of either the individual herbicide or mixturesof two herbicides in various proportions dissolved in a mixture ofacetone and water. The said weeds are Amaranthus retroflexus, Setariaviridis, Setaria faberi and Echinochloa crus-galli.

[0032] Two weeks after treatment the percent reduction in plant growth,compared to an untreated control, was assessed.

[0033] Control in one or more weed species was observed by combinationsof the present invention.

EXAMPLE 2

[0034] Seed of various weed species, as listed in Example 1, were sownand grown up to a 1-3 leaves stage. Post-emergence applications of arange of concentrations of either the individual herbicide or mixturesof two herbicides in various proportions dissolved in a mixture ofacetone and water were made.

[0035] Two weeks after treatment the percent reduction in plant growth,compared to an untreated control, was assessed.

[0036] Control in one or more weed species was observed by combinationsof the present invention.

[0037] According to a further feature of the present invention there areprovided herbicidal compositions comprising:

[0038] (a) 2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione,or an agriculturally acceptable salt or metal complex thereof; and

[0039] (b) a triazine herbicide with the exclusion of atrazine;

[0040] in association with, and preferably homogeneously dispersed in, aherbicidally acceptable diluent or carrier and/or surface active agent.

[0041] The term “herbicidal composition” is used in a broad sense, toinclude not only compositions which are ready for use as herbicides butalso concentrates which must be diluted before use. Preferably, thecompositions contain from 0.05 to 90% by weight of benzoylcyclohexanedione and triazine herbicide.

[0042] Unless otherwise stated, the percentages and ratios appearing inthis specification are by weight.

[0043] Generally a composition in which the ratio of (a):(b) is from1:6000 to 64:1 wt/wt of (a):(b) is used, proportions from 1:600 to 4:1wt/wt (or from 1:600 to 3.41:1 wt/wt) being preferred, with proportionsfrom 1:100 to 2:1 wt/wt (or from 1:100 to 1.33:1 wt/wt) particularlypreferred and proportions of from 1:20 to 1:1 wt/wt (or from 1:20 to1:1.33 wt/wt) especially preferred.

[0044] The herbicidal composition may contain solid and liquid carriersand surface-active agents (e.g. wetters, dispersants or emulsifiersalone or in combination). Surface active agents that may be present inthe h rbicidal compositions of the present invention may be of the ionicor nonionic types, for example sulphoricinoleates, quaternary ammoniumderivatives, products based on cond nsates of ethylene oxide with nonyl-or octyl-phenols, or carboxylic acid est rs of anhydrosorbitols whichhave been rendered soluble by etherification of the free hydroxy groupsby condensation with ethylene oxide, alkali and alkaline earth metalsalts of sulphuric add esters and sulphonic acids such as dinonyl- anddioctyl-sodium sulphono-succinates and alkali and alkaline earth metalsalts of high molecular weight sulphonic acid derivatives such as sodiumand calcium lignosulphonates. Examples of suitable solid diluents orcarriers are aluminium silicate, talc, calcined magnesia, kieselguhr,tricalcium phosphate, powdered cork, absorbent carbon black and clayssuch as kaolin and bentonite. Examples of suitable liquid diluentsinclude water, acetophenone, cyclohexanone, isophorone, toluene, xylene,and mineral, animal, and vegetable oils (these diluents may be usedalone or in combination).

[0045] Herbicidal compositions according to the present invention mayalso contain, if desired, conventional adjuvants such as adhesives,protective colloids, thickeners, penetrating agents, stabilisers,sequestering agents, anti-caking agents, colouring agents and corrosioninhibitors. These adjuvants may also serve as carriers or diluents.

[0046] The wettable powders (or powders for spraying) usually containfrom 20 to 95% of benzoyl cyclohexanedione and triazine herbicide, andthey usually contain, in addition to the solid vehicle, from 0 to 5% ofa wetting agent, from 3 to 10% of a dispersant agent and if necessary,from 0 to 10% of one or more stabilisers and/or other additives such aspenetrating agents, adhesives or anti-caking agents and colourings.

[0047] The aqueous suspension concentrates, which are applicable byspraying, are prepared in such a way as to obtain a stable fluid product(by fine grinding) which does not settle out and they usually containfrom 10 to 75% of benzoyl cyclohexanedione and triazine herbicide, from0.5 to 15% of surface acting agents, from 0.1 to 10/o of thixotropicagents, from 0 to 10% of suitabl additives such as antifoams, corrosioninhibitors, stabilisers, and water or an organic liquid in which theactive substance is sparingly soluble or insoluble. Some organic solidsubstances or inorganic salts can be dissolved in order to assist inpreventing sedimentation or as antifreeze for the water.

[0048] Preferred herbicidal compositions according to the presentinvention are wettable powders and water-dispersible granules.

[0049] Herbicidal compositions according to the present invention mayalso comprise a benzoyl cyclohexanedione and triazine herbicide inassociation with, and preferably homogeneously dispersed in, one or moreother pesticidally active compounds and, if desired one or morecompatible pesticidally acceptable diluents and carriers. Preferredherbicidal compositions according to the present invention are thosewhich comprise a benzoyl cyclohexanedione and a triazine herbicide inassociation with other herbicides.

[0050] The compositions of the invention may be made up as an article ofmanufacture comprising a benzoyl cyclohexanedione and a triazineherbicide and optionally other pesticidally active compounds ashereinbefore described, and as is preferred, a herbicidal composition ashereinbefore described and preferably a herbicidal concentrate whichmust be diluted before use, comprising the benzoyl cyclohexanedione andtriazine herbicide within a container for the aforesaid benzoylcyclohexanedione and triazine herbicide or a said herbicidal compositionand instructions physically associated with the aforesaid container,setting out the manner in which the aforesaid benzoyl cyclohexanedioneand triazine herbicide or herbicidal composition contained therein, isto be used to control the growth of weeds. The containers will normallybe of the types conventionally used for the storage of chemicalsubstances and concentrated herbicidal compositions, which are solids orliquids at normal ambient temperatures, for example cans and drums ofplastics materials or metal (which may be internally-lacquered), bottlesof glass and plastics materials; and when the contents of the containeris a solid, for example a granular h rbicidal composition, boxes, forexample of cardboard, plastics material, metal or sacks. The containerswill normally be of sufficient capacity, to contain amounts of theactive ingredients or herbicidal compositions suffici nt to treat atleast one hectare of ground, to control the growth of weeds therein butwill not exceed a size which is convenient for conventional methods ofhandling. Instructions will be physically associated with the container,for example by being printed directly thereon or on a label or tagaffixed thereto. The directions will normally indicate that the contentsof the container, after dilution if necessary, are to be applied tocontrol the growth of weeds at rates of application from 0.5 to 512 g ofbenzoyl cyclohexanedione and from 8 to 3000 g of triazine herbicide perhectare in the manner and for the purpose hereinbefore described.

[0051] The process described in U.S. Pat. No. 5,006,158 may be used toprepare the benzoyl cyclohexanedione of formula (I).

[0052] According to a further feature of the present invention, there isprovided a product comprising:

[0053] (a) 2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione oran agriculturally acceptable salt or metal complex thereof; and

[0054] (b) a triazine herbicide with the exclusion of atrazine;

[0055] as a combined preparation for simultaneous, separate orsequential use in controlling the growth of weeds at a locus.

[0056] While the invention has been described in terms of variouspreferred embodiments, the skilled artisan will appreciate that variousmodifications, substitutions, omissions, and changes may be made withoutdeparting from the spirit thereof. Accordingly, it is intended that thescope of the present invention be limited solely by the scope of thefollowing claims, including equivalents thereof.

1. A method for controlling the growth of weeds at a locus whichcomprises applying to said locus: (a)2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione, or anagriculturally acceptable salt or metal complex thereof; and (b) atriazine herbicide with the exclusion of atrazine.
 2. A method accordingto claim 1 wherein the triazine herbicide is a compound of the formula(II):

wherein R¹ represents chlorine or straight- or branched chain alkylthioor alkoxy having from one to six carbon atoms; R² represents azido,monoalkylamino, dialkylamino or cycloalkylamino, in which the alkyl orcycloalkyl moieties may be optionally substituted by one or moresubstituents selected from cyano and alkoxy, and R³ representsstraight-or branched-chain N-alkylamino having from one to six carbonatoms; or of formula (III):

wherein R¹ is as defined above and R⁴ represents straight- or branchedchain alkyl having from one to six carbon atoms.
 3. A method accordingto claim 2 wherein in formula II, R² represents azido, straight- orbranched-chain N-alkylamino having from one to four carbon atoms(wherein the alkyl moiety is optionally substituted by cyano or method).4. A method according to claim 1 or 2 wherein the triazine herbicide isselected from: simazine, which is6-chloro-N²,N⁴-diethyl-1,3,5-triazine-2,4-diamine; and cyanazine, whichis2-(4-chloro-6-ethylamino-1,3,5-triazin-2-ylamino)-2-methylpropionitrile.5. A method according to claim 4 wherein the triazine herbicide iscyanazine.
 6. A method according to claim 1 or 2 wherein the triazineherbicide is metribuzin, which is4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one.
 7. A methodaccording to any one of the preceding claims in which the applicationrate of benzoyl cyclohexanedione is from 5 g to 500 g per hectare andthe application rate of triazine herbicide is from 250 g to 5000 g perhectare.
 8. A method according to any one of the preceding claims inwhich the application rate of benzoyl cyclohexanedione is from 25 g to150 g per hectare and the application rate of triazine herbicide is from500 g to 1500 g per hectare.
 9. A method according to any one of thepreceding claims for the control of grass weeds in maize.
 10. A methodaccording to any one of the preceding claims wherein the compounds areapplied pre-emergence of the weeds.
 11. A herbicidal compositioncomprising: (a) a benzoyl cyclohexanedione derivative of formula I asdefined in claim 1, or an agriculturally acceptable salt or metalcomplex thereof; and (b) triazine herbicide with the exclusion ofatrazine; in association with a herbicidally acceptable diluent orcarrier and/or surface active agent.
 12. A herbicidal compositionaccording to claim 11 wherein the ratio of (a):(b) is from 2:1 to 1:1000wt/wt.
 13. A herbicidal composition according to claim 11 or 12 in whichthe ratio of (a):(b) is from 1:4 to 1:60 wt/wt.
 14. A product comprising(a) benzoyl cyclohexanedione of formula I as defined in claim 1, or anagriculturally acceptable salt or metal complex thereof, and (b) atriazine herbicide with the exclusion of atrazine, as a combinedpreparation for simultaneous, separate or sequential use in controllingthe growth of weeds at a locus.